20 STARCHED 



(16) Arum Starch. 



This starch, formerly obtained at Portland from the rhizomes 



Arum maculatum, Linn., and known as Portland arrowroot, is no 



onger an article of commerce. It is, however, still prepared in 



Southern Europe and Northern Africa in small quantity from 



A. maculatum and other species of Arum. 



The grain of arum starch are originally compound, but they 

 generally occur isolated in the dry starch. Most of them, there- 

 fore, possess one or moro flat surfaces. Some are hemispherical or 

 conical, others curved on one side and provided with two flat sur- 

 faces on the other. The large grains seldom exceed 21,u in length ; 

 many grains measure from 7 to 15/i, and the smaller ones, 3 to 7jit. 



(17) Tacca Starch 



Is obtained from the tubers of Tacca pinnatifida, Linn., and is 

 also known as Tahiti arrowroot. 



The grains vary both in size and shape. Typical ones are 

 rounded, oval or even lenticular; some are elliptical, almost 

 triangular, etc. The hilum is generally fissured, situated near the 

 centre of the grain, and surrounded by concentric strise. The 

 larger grains measure 38 to 50u, the smaller 15 to 25/*. 



